By general consensus, Robert Rauschenberg is one of the most important artists of the 20th century. Yet, he has the most erratic market of any major artist. The reason why is that his imagery is hard to describe and even harder to retain once you've seen it. Rauschenberg generally creates paintings with a glut of disparate images. He collages snippets of daily life that might make sense visually but often fall short conceptually -- unless you buy into the artist's philosophy that the entire world is his palette.

Anyone who has ever read an art history book can tell you that both Rauschenberg and Jasper Johns provided a link between the macho paint handling of the Abstract Expressionists and the popular imagery of the Pop artists. Rauschenberg's approach was to join the two styles to create a new hybrid. He covered the surface of his works with found objects, magazine reproductions and newspaper clippings. Then he attacked the assemblage with dripping brushstrokes that tied the picture together. These works became known as the Combines. They're rare at auction and consistently bring million-dollar-plus prices.

In this writer's opinion, Rauschenberg's strongest works are the Silkscreens of the 1960s. Borrowing the technique from Andy Warhol (Rauschenberg gives him full credit), he used overlays of photo silkscreen images to reflect the times -- contemporary icons such as John F. Kennedy and the Apollo space capsule. Once again, the Silkscreens are scarce at auction and often bring seven-figure prices.

During the mid-1980s, Rauschenberg began juxtaposing key elements of the Combines and the Silkscreens. He began silkscreening images on the shiny surfaces of sheets of metal, such as stainless steel, copper and aluminum. He also splashed on some paint and, for good measure, would sometimes even adhere a found object or two. Rauschenberg called the new works "Shiners, Gluts, and Urban Bourbons."

The series garnered a lot of press when it was shown at Knoedler & Co. but never sold well. However, these "paintings" are probably his most undervalued works. In fact, they are some of the most undervalued works in the entire contemporary art market. A large example, say six by eight feet, can often be bought at auction for under $150,000. Smaller works bring between $60,000-$85,000. Think about it -- this is for a full-blown painting by one of the giants of art history.

Another buying opportunity is Rauschenberg's Transfer drawings from the late 1950s and 1960s. Ever the inventor, he would take an image from a color magazine, pour lighter fluid on it, and then use a blunt instrument to rub it onto a sheet of paper. The result was a drawing that felt like one of his paintings, only more delicate and ethereal. The drawings with multiple recognizable images are the real gems.

What's more, lately they have been doing well at auction. Until recently, the going rate for a Transfer drawing was $65,000-$200,000. Not that long ago, at Sotheby's (May 2000), a drawing sold for $291,750. Proving that was no fluke, that same week at Sotheby's (Part I), a drawing that featured Jackie Kennedy sold for a record $473,250.

In the 1990s, Rauschenberg began experimenting with a different sort of transfer imagery that resembles decals. Most of these paintings rehashed previously covered ground. The only difference is that they are soft-focus and almost Impressionist-like. He also returned to canvas. Perhaps it was a coincidence, but he began producing these works right around the time he began working with PaceWildenstein. But whatever the case, Rauschenberg started selling work again. Even if you're a superstar, you still need funds to operate, especially if you are as ambitious as Rauschenberg.

What does the future hold for his market? With the death of Roy Lichtenstein, Rauschenberg remains one of the few art gods still alive and working. Collectors should not be put off by the seeming availability of his work. Although Rauschenberg is prolific -- probably in the Andy Warhol or Sam Francis category -- his better works are hard to find.

As collectors continue to squander money on the big names that came out of the 1980s, they could just as easily buy a Rauschenberg (from the same period) for much less. This will not always be the case -- sooner rather than later.